Hydraulic power system



NOV. 17, 1953 H, Q CONWAY ETAL v l 2,659,204

HYDRAULIC POWER SYSTEM Filed Nov. 18, 1950 2 SheelZs-Shee'lI 1 F' ,j/21314 Wij/01620015 JACK ARGE VOL ME l Mf'a//v pz/Mp u VALVE msm/eurosj] 40 /22 Z) 20 M0702 35 gb-s Nov. 17, 1953 H. G. coNwAY ET Al.2,659,204

HYDRAULIC POWER SYSTEM Filed Nov. 18, 1950 2 Sheets-Sheet 2 l y V15575d. 30 [L l NM f f77 L L@ j@ Z [if mi' O .them to prevent trouble.

Patented Nov. 17, 1953 Hugh Graham Conway,

Fairclough, Gloucester,

Societe dInventions ques S. I. A. M., Genev ration of Switzerland GeorgeOrloff, and Roy England, assignors to Aeronautiques et Mecania,Switzerland, a corpo- Application November 18, 1950, Serial No. 196.474

This invention comprises-improvements in or relating to hydraulic powersystems. It is lan object of the invention to provide means Where- -byexcessively low temperature of the system is prevented Whether freezingup, vor such` thickening of the hydraulic liquid interferes with properoperation of the system. While the system herein described isparticularly applicable to aircraft, where low temperature presents anespecial problem, the system is also capable of being applied inotherconnections.

According to the present invention, an hydraulic system is provided withcontrolled leakage in an operated element or elements of the system, theleakage being adequate to provide such heat as is necessary under normalworking conditions to preventl such excessively low temperature of thesystem; Wherever leakage occurs in an hydraulic system, heat isnecessarily generated due to the waste of energy. It is the operatedelements of the system which are normally liable to become frozen or putout of practical operation by thickening of the hydraulic medium, and byproviding controlled leakage in these elements sufficient energy is setfree in comme. (c1. lso- 52) The resultant 'ow of hydraulic fluid fromthe Vpump and on return to l the reservoir clear.

In'order to prevent Waste of energy when the operated elements of thesystem are-being used, the leakage is preferably effected through. aleakage channel or channels which are vonly open When vthe operatedelement or elements .are in a normal position of rest. For example,there may be an operated element in the form of ajack of the system alsokeeps theppes 'and the'leakage channel may comprise-a leak-V age portopened automatically by the jack-piston on .reaching the end of itsstroke.` Preferably the leakage channel is located in the piston itselfand -closed by :a lift-valve, in` the piston, which valve isL openedyautomaticallyby.tappet1action when the pistonreaches one end lofitsstroke.,

In one `form of the-system according tothe present invention, anauxiliary pump is provided of `capacity adequateto s upply the leakage,vin

addition to the main supplypumpjvofvthesystem.

. The auxiliary pumprcanbe kept runninghfwhen Vthe parts are in theirVnormal ,positionsgof rest 'and win supply the energy-necessary tn.prevent 'freezing'upvwhile Atlriemain pump Will be set in operation.whenV the parts, Vare' tobev actuated. i This obviates using the-largepump continuously, which Ywould' be disadvanta'geous. rbecause eitherexcess-j energy. would Y have. lto be'k hWasted orflth PumpWpuldheveiwbekspt #tewater Quand off load for the whole time, andnotonly when parts are to be actuated. l r

In an alternative form of the system according to the present invention,the by-pass to the main pump delivery is provided with throttling meansunder thermostatic control with the object of ensuring that. sufcientheat is developed to keep the liquid in the main supply tank at asuitable temperature. I f

Preferably, in a jack constructed fas above described, in addition tothe said valve there is a fixed leakage aperture of 'restricted boreprovided' in series with the valve so that Whenthe valve is opened asubstantial proportion of the pressuredrop through the leak takes placeat this aperture. The pressure drop across the restricted aperture isproportional to the square of the velocity of flow therethrough..V Iftherefore the aperture itself should become. partly `frozen up and sorestricted further, the eifect will be to raise very substantially(morethan in direct pro- Y portion ,to the degree of restriction) thepressure lon thereceiving side of the aperture,'assuming the normal typeof.pump is employed for producing'the pressure, which has asubstantially constant rate of delivery, .irrespective of pressure, at agiven speedof operation. The result is1increased power applied at theaperture, and increased evolution of heat,;.so thatthe'aperturespill-valve-and acts to ensure maximum energy l dissipationTherspill-valve 'also automatically jack is operatedjinthe-'reversedirection.

prevents return flow through 'the leak Iwhenthe The Afollowing is'vadescriptiony by W'ayf'o'f-'example j' of specic v"constructions 'in'accordance l Wtlfr theinvention'.` .v Y

In the acc'ompnying'drawmss Figurefl tiene?)Y Y l Figure A1a isjauetaiivtoianeniarged scale o fa Apart of said diagram;

Figure 2 miami section-ihatgiia end of ajack construted, .go jmurat@nacco'rr Y.

ance with the present invention y yFigure Sis afsimilar'lview-,ofanotherfjack; .Y Y Figures lLand uare similaryiews of; alternativeFigures isfalceieidielnietig-an eiiar showing' such a Y i on the by-passfrom the auxiliary pump30 if desired instead of or in addition tooperating on the by-pass from the main pump Il.

Figures 2 to 6 show various forms of jack for use as the jack I6 shownin Figure 1. Referring to Figure 2 this shows a jack cylinder I 5containing a piston 24 which is`connected to a hollow jackl rod 25. Theytappetsystem which corresponds to the valve 21 and tappet 28 of Figure 1is arranged to operate in this case when the jack is extended, that isto say when it reaches the end corresponding to the pipe I9 of Figure 1.In the piston 24 is an axial bore 50 which is divided bya bushing 5Ifrom a second axial bore 52. Through the bushing there is a passage 53which constitutes a leakage aperture and in which is loosely fitted avalve 54 corresponding.

to the valve 21 of Figure 1. The valve 54 is closed by a light spring 55beyond which is a screwed plug 55 containing a narrow leakage aperture51.

On the other side of the bushing 5I there is a v valve-lifting member 53which engages'the stem of the lift valve 54 and which is backed up by aspring 59 which is stronger than the spring 55. Beyond the valve-liftingmember 58 there is a tappet member 60 which backs up the spring 59,slides to and fro in the bore 50 and is connected by a cross pin 6I to atappet sleeve 52 which surrounds the piston rod 25 and is capable ofsliding thereon due to a slot 63 in the piston rod 25 through which slotthe pin 5I passes.

The valve lifting member 58 is conical at its end portion as shown at 64and the conical end portion of the lifting member can seat upon thematerial of the valve 24 surrounding the bushing 5I to block the leakageaperture 53 on the side remote from that upon which the head of the liftvalve 54 seats. From the space around the conical end of the valvelifting member 58 there extends a passage 65 to the side of the piston24 which is open to the-pipe I9.

If the jack, with its piston so constructed, has a normal position ofrest in which it is extended, that is to say with the piston rod 25fully pushed out of the jack as shown in Figure 2 of the drawing, thetappet sleeve 62 .engages the end of the jack cylinder IB where itsurrounds the hollow piston rod 25 and pushes the tappet member 59 tothe left as viewed in the drawing, compressing the spring 59 and causingthe Valvelifting member 58 to push the lift Valvel 54 olf its seat asshown. The valve 54 at first resists being pushed ofi" its seat but thetappetl 50 can engage the end of the valve-lifting member 58 when thespring 59 is compressed and will so force the valve off its seatV afterwhich the spring V59 expands again and pushes ther valve 54 fully open.l

The conical end 54 of the valve lifting member'4 58 tends to seat on thebushing 5I but pressure fluid coming through the aperture 51 forces theconical end a little way olf itsseat and leakage takes place insuccession through the aperture 51, the

leakage aperture 53, past the conical end 6,4 and through the passage Vto the pipe I9. The

valve-lifting member 58 acts as a spill-valve in series with the leakageapertures 51, 53 and increases the total pressure loss when there is aconsiderable pressure drop through the aperture 51, that is to say ifthe viscosity of the liquid is high due to low temperature. Y

Referring to Figure 3, this shows a similary construction for the casewhen the leakage through the piston is to be controlledr from the otherend of the jack, that is1to say the-end vremote from that at which thepiston rod v25 Vend pressure exerted by plug 12 containing a narrowleakage aperture 13,-, and corresponding in function to the plug 550i.'Figure 2, is provided inthe end of the passage 65.A

The operation is the same as Figure 2.

Referring to Figure 4, partof this corresponds1 to Figure 2 and as faras possible similar parts: are similarly numbered in thedrawing andwill. However,` ball valveaccordingly not be further described. insteadof the lift valve 54 there is a 15 which floats between the two springs55, 59= and the valve lifting member 58 is done awayl with.- The .ballValve 15 floats in an enlarged'. portion 16 of the bore 50 betweenseatings 11, 18.. When pressure in the jack cylinder I5 is urging thepiston to move from the left hand end of the jack towards the positionshown in the draw ing the tappet sleeve 62 will be pressed towards; theright hand end of the slot 63, the compression of the spring 55 will berelaxed and the pressure in the cylinder I5, acting through the bore -51will press the valve 15 on to the seating 11 and prevent leakage ofhydraulic liquid through the piston. When the tappetv sleeve 62 engages'the end of the cylinder and the valve lifting member 5@ is held frommovement with the piston, the end of the valve lifting member'. S0engages the ball i5 and also compresses the spring 59 and pushes theball 15 off-the seat l11. After this the ball 15 acts as a spill-Valveagainst the seat-` ing 18.

Precisely the same action takes place in Figure 5 where, however, thetappet member y(il) directly engages the end of the cylinder I6 and theparts are modified as compared with Figure 4 in the'- same way that thep-arts of Figure 3 are modified as compared with Figure 2. y

:Referring-howto Figure 6 this shows al con-V described intheaforesaidpatent specificationl No. 527,225, and that these engage alocking sleeve 8i held in the end of the Vcylinder I6 by an end capisecured on the cylinder I5. The end cap contains a bore 83 for alocking piston 84 which is urgedforward into locking position by astrong spring 85. The locking piston 84 is provided with a cylindricalbolt portion 85 which, as shown in the drawing, when the crown of thelocking teeth or claws 85 are pushed fully home through the lockingsleeve 8|, is able the space within the crown vof locking claws and toprevent them from withdrawing. The springpressed bolt 86 constitues ineffectl the end of thel jack cylinder and 'it is against the end of thisbolt that the tappet member engages. The valvemembjer instead of beingconstituted to shoot forward into hir .9.- buil l! is acnettuied lav edeubleeeoned eigener .8l whien plays, hetneenseetinea 11, 1,18 and aeten; 88. te engage an intermediate niemeer QS which pressed sindireetlv by the Serine. 59. .and is: Qpereted.. bv the tappen memberlll-The pesseee. Si represented. in Eiern@ ti 9v fletes 9.0 cui. the @inside0i the tapnetixneni, ber 6 and. the resirieted anemie .i1 ie farmed l.ee 5.6 on the. mesme VSide vf the' valve merel? 81 insteasi er reime@ a,eine. Slick as. l2 011 the eige marient@ Paseages Si! in fille Wells Qithe @New pieton red .25 'Peimit M0855. Qi the hld. lic mi@ t9 the:various Paaess. end; velvee Thev Qeeiatiqnthe .seme *Q6/folliaReiellfirie te Een@ il., @his .snows e nel: me having. e Pieten iloperates e hollen leek. mi... .we leakage is nr d. ier by means @freeerieree H95: ihelale. 'W lead t0 e S12-eee. Sheieel .lied Wlhieliis ineornmunif @eilen 1w e..peseee @0i with.' the: leakage aner-y tnre it...'Elie pie-estre@ i104 is; @entrai-lee by naive and. the4 valve: le bn a.valve red. lill" te the; @oxe- LQS oiaseleneie me... The salenoidis@exalted by eleetiiieai .naect 4mi., .H1-which sees: Gemeen the .ieeerod; and. ,are .cpnneeted to ein! Suitable centrali. .The ieakeee.passage me s desee., te the action of a spring. IJ .3 wliihf @loseethevalne. m6 until the vselezioni. |593 ,ie enenginagi.A een.befarranged te be ai. ieetel einer autpmatieallvwhen the. nistnn laireaches ille-.enel oi itsstmleor: under the central .et endetenthermstatiallvbmatemneratmzeqenimllee switch: ar.- lzy; e; -enibinatipnof; s uch mainbedesired.

.In lira inet-in omeaincnatvit may bedesirable to. prev-irl@ additinnalmeans for heating; variaus; vente furthe; eineuitiwheratne. pines. pass.throne-li. particularly cold parts of the aircraft. This. may be dene;electriiallx Iim'.willemise, as .desi-red.

.1r-.In a hldlaui. imiterl system including: a.y Hillman intermittentlyv`operative cirm:u't.iory nunk medium. lla-ving. a. main circulatingpump and.' drive motor therefor.` innluded;` theueinf, `a sec-- Onify;CiIZQuit the medium having an auxiliary: 911.11ml Aand drive: motortherefor invcludeliliherein;.Selectiuelyfoperableimanual:means;rendering said .seennidanvr` circuiti inoneratiivrei when, Said` primary.circuiti is operative andi Rendering-...said secondary circuit.operative. when seickprmarxgeincuit -isinoperative and a jaeny having;a. dvlinden `eQnneeted-ctu said means .andl a. piston; alicia-ble.A in..the cylinder, the .provision of' means .011 .maintaining the uidmedium; insaid.y

secqndary cireuit` when. uperative:- at a desired:

werking temperature, saidl last, meanseornpris ing aleakage channel@in'. the piston, aV lift valve in the pieten .constructed and arrangedte close the channel at; all pesitions of' the .piston other than apredetermined end position. in the eylinfn der, means. fm: said valvewhen the. piston at. said predetermined end position, and a, xed leakageaperture in the cylinder of re.- stristed bore in series with said liftvalve.

2. In ahydraulic power' system including a primaity intermittentlyoperative circuit` for fluid medium having a circulating ypumpy anddrive motor tnerefmv included therein, a. sec: ondany circuit for thefluid medimn having an auxiliary' pum-p and drive motor therefor in-vcluded. i;lieizezrn,` selectively operable manual means rendering saidisecdndary .circuit inoperative `\v,hen said primary' is operative andvrendering said seeolzrdary circuit operative when said primary .circuitiis inoperative, andv a. jack. a cylinder connected tu said means and aypiston `slida'blej in. the. evlinder, the provision .of ineens forAmaintaining the fluid medium in said; secondary circuit when operativeat a desired working temperature', said last means comprising a.leakauge` channel in the piston, a lift valve in the. piston construetedand. arranged to close the channel at all nesitions @i the piston .otherthan a predetermined end. position in the cylinder, a stern projectingfrom said, lift valve. beyond said. piston toward the end` of said.cylinder corre..- Snoilding. to; said end. position of the piston, a xedleakagepaperture in. .the cylinder .of restricted herein. series withsaidf. lift valve,v .a .spill valve in series with. .sa-id. aperture.l:and spring-y means urgina said spil-l valve to. ,closed position..

GRAHAM QGNWAY.

GEQRGE' ORLOFF.

FARGLQUGH- Beierenees Cited in the file .of this. patent.

UNIfIaFlD. STATES PATENTS.

Number' Name Date 1,520,035 stones Aug. 25, 193i 13904.-,345 Anthony etal Apr. '18, 1933 alize-,aessmith Jan. '1, i936 213713505"- Anthonyr etal. Feb; 23, 1937 2,;146366 v Anthony et al. Feb. 'A 1939 2,166,940Gon'rad'sene r July 25, 1-989 aesinet Wylie sept. 29, 1942 l2;,-9ia3'r5`Herma-n T -e Mar. '1, 194e -2',? 55',669 Moser V Y Aug. 15; 1944' 2&'43,989A Rockwell Mar; 6, 1951l 25m-333 zwael: Y June 193 19e-1 12,55l;334f Zweck' June 19-,-1'951 FOeElGN PATENTS Number.. A CountryfDate BfOABs Geteat Britain Nov. v2, 1931

